1. Field of the Invention
The present invention relates to systems adapted to control lighting intensity.
2. Description of the Related Art
In some environments, for example in the interior of motor vehicles, lighting elements of several different technologies may coexist. On the instrument panel of a vehicle, for instance, switches may be back-lit with incandescent lamps while containing light-emitting diodes which act as enunciators to indicate when the respective switches are turned on. All of such lighting elements are typically dimmable at the control of the vehicle's driver, through the driver's operation of a rheostat.
Where lighting elements of different technologies coexist, a concern arises where the lighting elements of different technologies have different lighting intensity versus applied voltage characteristics. Where this is the case, such as with incandescent lamps and light-emitting diodes, it is difficult to control the intensity of the different lamps uniformly over their entire intensity ranges. Non-uniform relative intensity of the lamps can be the result. This is a potential source of customer dissatisfaction in a vehicle whose interior is carefully designed to have a highly refined appearance.
One way to overcome the different intensity versus applied voltage characteristics of different lighting technologies is to use a microprocessor to apply different lighting transfer functions to the lighting elements of different technologies. The different transfer functions compensate for the different intensity versus voltage characteristics of the lighting elements. However, this solution is not totally satisfactory, as different intensity control circuits are needed for the different lighting elements. This can add cost. Also, microcomputer resources are fairly expensive, so using a microprocessor to individually calculate several lighting transfer functions can be costly.
Therefore, a system which can provide modify the intensity versus voltage characteristics of lighting elements more cost-effectively than the prior art will prove advantageous.